Method and apparatus for making measurements of accumulations of magnetically susceptible particles combined with analytes

A method for quantitatively measuring analytes using magnetically susceptible particles, comprising:

• applying at least one sample on a sample holder, the sample including a plurality of bound complex particles, each bound complex particle including an analyte combined with a magnetically susceptible particle;
• creating a magnetic field;
• inductively exciting the magnetic particles in the sample with the magnetic field to cause oscillations of the magnetizations therein;
• sensing the fields generated by the oscillating magnetizations, wherein the sensing includes sensing the fields using a sensor connected in a gradiometer configuration, and wherein the sensor has a sensing area substantially the same as an extent of the sample;
• and
• creating a signal representative of the sensed field.

An apparatus capable of quantitative magnetic measurement of samples, comprising:

• a sample holder to contain a plurality of samples, each sample including combinations of analytes and magnetically susceptible particles;
• a magnetic field source to apply an alternating magnetic field to the samples, the magnetic field source defining a gap in which the sample holder may be disposed;
• a substantially flat magnetic field sensor to sense an induced magnetic moment from the samples and configured and arranged in a gradiometer configuration to substantially eliminate the contribution of the magnetic field source to the sensing, the magnetic field sensor having an output to communicate output signals, the magnetic field sensor disposed substantially within the gap of the magnetic field source, the magnetic field sensor having a sensing area substantially the same as the extent of a sample;
• and
• an electronic signal processor to process the output signals from the magnetic field sensor to provide a signal indicative of the quantity of the samples in the pattern.

An apparatus capable of quantitative magnetic measurement of samples comprising:

• a sample holder to contain an extent of a plurality of samples including combinations of analytes and magnetically susceptible particles;
• a magnetic field source to apply an alternating magnetic field to the samples, the magnetic field source defining a gap in which a sample holder may be disposed, the gap having a width of less than about 5 mm;
• a substantially flat magnetic field sensor to sense an induced magnetic moment from the samples and configured and arranged in a gradiometer configuration to substantially eliminate the contribution of the magnetic field source to the sensing, the magnetic field sensor having an output to communicate output signals, the magnetic field sensor disposed substantially within the gap of the magnetic field source and having a sensing area substantially the same as the extent of the plurality of samples and having a dimension of the sensing area greater than a spacing between the plurality of samples and the magnetic field sensor;
• and
• an electronic signal processor to process the output signals from the magnetic field sensor to provide a signal indicative of the quantity of the samples in the pattern.

An apparatus capable of quantitative magnetic measurement of samples, the samples each including a plurality of combinations of analytes and magnetically susceptible particles, each sample arranged in a pre-defined pattern and disposed in a sample holder, comprising:

• a magnetic field source to apply an alternating magnetic field to the sample, the magnetic field source defining a gap in which a sample holder is movably disposed, the magnetic field source including an electromagnet with a magnetically permeable core whereby electromagnetic flux is directed in a predetermined manner to the sample;
• a substantially flat magnetic field sensor to sense an induced magnetic moment from the sample and configured and arranged in a gradiometer configuration to substantially eliminate the contribution of the magnetic field source to the sensing, the magnetic field sensor having an output to communicate output signals, the magnetic field sensor disposed substantially within the gap of the magnetic field source;
• and
• an electronic signal processor to process the output signals from the magnetic field sensor to provide a signal indicative of the quantity of magnetic material in the sample.